1. Field of the Invention
The present invention pertains to devices for cutting elastomeric materials; and, more particularly, pertains to such devices for in situ sampling of specimens of solid propellant in rockets.
2. Description of the Prior Art
Large, military, solid propellant, rocket motors must be stored for decades and yet function with full effectiveness. To ensure this effectiveness, samples of the propellant may be taken regularly from substantially complete serviceable or specimen motors for testing to determine if the propellant has remained stable. The propellants of interest are elastomers which are very tough and highly elastic so as to retain their shape and function despite shocks in transportation and the intense vibrations and thermal stresses that occur following ignition. The propellant is, typically, a single large "grain" cast within a generally cylindrical casing having a smaller nozzle opening at one end from which a central cavity extends axially into the grain. This grain may include "fins" disposed circumferentially about and extending axially within the cavity.
Such tough and highly elastic propellants are difficult to cut since they compress rather than sever when subjected to a pressure from a cutting edge and since their elasticity induces oscillations when subjected to such pressure. Further, the necessary samples may be required from regions deep within the cavity and may require cuts along planes not parallel to the axis of the cavity.
Because of the mechanical properties of such elastomeric propellants, the large size of the motors and samples, and the relative inaccessibility of the propellant through the cavity, there has been heretofore no satisfactory remotely controlled, powered device for obtaining the necessary specimens; and the hazard to personnel resulting from ignition or detonation due to cutting energetic materials has been accepted by excising specimens of such propellant fins manually by a spade-like cutting device.